Research Briefing

Bacterial motors respond to chemical signals with high sensitivity to control cell swimming behaviour. However, the established model that describes how this sensitivity arises is an equilibrium model, which is inconsistent with experimental findings. A model is now proposed in which high sensitivity results from non-equilibrium mechanical interactions within the motor.

In most metals, free electrons form a homogeneous and isotropic fluid. However, a periodically modulated electronic fluid — known as a liquid charge density wave — is thought to form when electrons interact strongly with the vibrations of the crystalline host. This state is now observed using ultrafast electron diffraction.

An electrical method is shown to reliably introduce nonreciprocal behaviour across a Josephson junction made of high-temperature cuprate superconductors, which then, under microwave irradiation, forms a ‘quantum superconducting diode’. The device is magnetic-field-free, works at a temperature of 77 K with a diode efficiency of 100%, and, owing to Shapiro steps that quantize the output voltage, has robust noise-filtering.

Adding momentum mixing in a controllable way to the exactly solvable Hatsugai–Kohmoto model is shown to recover the physics of the Hubbard model, the starting point for understanding Mott physics. The scheme converges as the inverse square of the number of steps, and, as each step is tractable, minimal computational resources are required.

In a heavy-fermion material, hybridization of conduction electrons and electrons in partially filled core-levels enhances the mass of charge carriers. Now, experiments using a two-dimensional heavy-fermion material show that the hybridization can be extremely anisotropic, with the result that the effective mass of charge carriers is direction-dependent.

In two types of roundworm neurons that can sense mechanical stimuli, the tension in the plasma membrane propagates rapidly, but it is spatially confined by periodic barriers formed by cytoskeletal and membrane proteins. This spatial restriction enables localized mechanical signalling, enhancing a neuron’s capacity to process multiple stimuli independently.

The microscopic magnetic textures of isospin symmetry-broken phases in rhombohedral tetralayer graphene have been directly imaged. By probing spin orientation and magnetic anisotropy at ultra-low fields, key energy scales — the spin–orbit coupling and intervalley Hund’s exchange — have been extracted, shedding new light on the phase hierarchy in strongly correlated electron systems.

Experiments that probe the spontaneously broken symmetries in rare-earth tritellurides have revealed a previously hidden ferroaxial density wave arising from intertwined charge and orbital order, which is observed to produce the axial Higgs mode.

Cells migrating through narrow spaces in their environment undergo repeated shape changes to pass through tight constrictions. Epithelial cells retain a memory of past confinement, allowing them to maintain a polarized, compact morphology that enhances future migration through narrow gaps. This memory is mechanically encoded in the actin cortex.

Quantum operations are modelled as unitary matrices, yet experimental implementations have been restricted to only a few gate types. This fundamental limitation has now been overcome using a scheme that combines frequency control with microwave driving, enabling universal implementation of arbitrary two-qubit operations.

Transport properties near the Dirac point in graphene are expected to be determined by quantum many-body interactions between relativistic electrons. Experiments now show that the flow of charge and heat in high-quality graphene close to charge neutrality can be described within a hydrodynamic framework, with universal intrinsic electrical conductivity that is quantized to a value close to the quantum of conductance.

Electron hopping on geometrically frustrated lattices leads to unusual, correlated phenomena, but materials whose structures match such lattices are rare. Now, in Pd₅AlI₂, frustrated electron motion is shown to emerge from the atomic orbital configuration, rather than the lattice geometry — which means the search space for unusual electronic structures and correlated behaviour can be broadened to materials with simpler, more common structures.

Bacteria can sustain spatial protein oscillations for a remarkably wide range of protein concentrations. The robustness arises from a conformational switch of a key protein between latent versus active states.

Symmetry breaking is routinely observed in isolated systems, where perturbations propagate through the system. For out-of-equilibrium systems, however, perturbations are predicted to diffuse; and this key signature of spontaneous symmetry breaking has now been observed in a polariton quantum fluid.

Photon interactions in materials typically create a gaseous bosonic state, which is prone to turbulent behaviour that disrupts coherence. But it is now shown that, using fast-gain processes in a modulated semiconductor laser, light can be stabilized in a liquid-like state, enhancing the coherence of its flow.

A two-dimensional spectroscopic technique to probe the strength of electron–phonon coupling has the capability to simultaneously resolve the phonon mode and the electron transition energy — and is bringing fresh insight into the complex interactions of phonons and electrons in a range of materials.

Second messengers are intracellular signalling molecules that relay environmental changes and prompt cellular responses. Through an information-theory framework coupled with quantitative experiments, the second-messenger molecule cAMP, in the bacterium Pseudomonas aeruginosa, is shown to achieve information transmission rates of up to 40 bits per hour.

Light-switchable enzymes hold great promise for mediating molecular activations in living cells, yet their full potential in realizing versatile controls in nonlinear networks remains unexplored. Now, optical control is demonstrated over a key enzyme involved in animal cell division, and a diverse array of dynamic cell shapes is achieved by biochemically hacking an endogenous signalling circuit.

Quantum electrodynamics (QED) is a cornerstone of the standard model of particle physics. A decade-long effort to simulate QED on a two-dimensional lattice has now succeeded — through the use of a trapped-ion quantum computer based on multidimensional ‘qudits’, which are uniquely suited to the challenge.

Ultra-low-temperature scanning tunnelling spectroscopy measurements indicate that twisting the layers in heterostructures making up a single layer of superconducting NbSe₂ on graphene leads to momentum-dependent changes in the superconducting gap. This ability could enable the development of artificial superconductors with nontrivial magnetic and topological properties.